Influence of surface roughness on thermography measurement
In this report, the theories of radiation and Signal-to-noise ratio (SNR) were explained, clearly. Also, two kinds of experiments were set up. One is focus on how the heating angle influence the thermography measurement, the other is focus on how the angle of the heating source, in relation to the crack direction and the direction of surface roughness, influence the SNR value.
The conclusions of these experiments are that the heating of a crack increases as the angle decreases (from wide side to narrow side) and the angle of increases (from horizontal to vertical). Moreover, the SNR value decreases as the surface roughness increases. For the same surface roughness, the SNR value increases with increased crack angle (0°, 45° or 90°) and with decreased sample position angle (horizontal, 45°or vertical). What is more, the higher surface roughness, the larger the influence of the crack angle and the sample position angle. Finally, when the surface is polish, the crack angle and the sample position angle does not have any influence.20209
Key Words: Emissivity; Surface roughness; thermography measurement; crack direction; direction of surface roughness
Preface
The author gratefully acknowledges University West for providing online library and the experimental equipment. The author thanks Per Henrikson who is working at GKN, for supplying the experimental samples. Specially, the author thanks Dr. Patrik Broberg for his technical assistance and guidance.
Contents
Preface ii
Symbols and glossary iv
1 Introduction 1
1.1 Background 1
1.2 Objective 1
2 Theory 1
2.1 Surface crack detection 2
2.2 Radiation 2
2.3 SNR 3
3 Literature survey 4
4 Experimental methods 7
4.1 Test sample 8
4.2 Experimental setup 10
5 Results 13
5.1 The results of the first experiments 13
5.2 The results of the second experiments 15
6 Discussion 16
6.1 The first experiments 16
6.2 The second experiments 19
7 Conclusions and future work 20
References 22
Appendices
A. Appendix A: The code for the first experiments
B. Appendix B: The data from the first experiments
C. Appendix C: The code for the second experiments
D. Appendix D: the original data from the second experiments
Symbols and glossary
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